Now a new study has shown that budgerigars can decipher sounds even if they've never heard someone speak before.

The research confirms that budgerigars understand and learn to copy speech cues in a similar way to humans.

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Budgerigars are known for their ability to mimic human speech, but no experience with human vocal sounds is necessary for budgerigars to perceive the difference between 'd' and 't', according to a new study. Pictured is one of the budgerigars used in the research

WHY CAN BUDGERIGARS PERCEIVE HUMAN SOUNDS?

Since birds can hear frequencies in a similar range as humans - meaning they can hear frequencies in the same range as what is in human speech - people can test how they respond.

There is something about human and bird auditory systems that integrates spectral and temporal information in a similar way.

Birds communicate with one another using sounds that also span the same frequencies as human speech (but also extend beyond what humans can produce).

The results of the study suggest they use the same type of mechanism as humans to perceive these kinds of sounds.

In the study, researchers from The State University of New York, Buffalo, found that the birds needed no experience with human speech to perceive the difference between 'd' and 't' sounds.

'Budgerigars are social animals, like humans, who communicate with other budgerigars with sound, and are motivated to interact with humans,' study lead author Mary Flaherty told MailOnline.

'We don’t have a clear understanding of how humans are able to perceive speech sounds due to how complex speech is - it’s an unresolved debate as to what mechanism is behind it.

'Budgerigars give us a way of really limiting auditory experience in order to examine the impact of “no speech” vs “lots of training on speech” to see if their perception would be altered based on their experience.'

Learning that a nonhuman animal can recognise and perceive speech in a way that is similar to humans gives us insight into how this works for humans, she said.

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But other evidence supports an auditory mechanism, which holds that, in the absence of extensive experience with speech, there should be no difference between speech and non-speech perception.

To investigate this latter scenario, the researchers divided 25 budgerigars into groups before hatching.

The team raised some in complete isolation from human speech and others with extensive exposure to human speech.

Budgerigars are vocal mimics that are similar to people in their ability to perceive consonant and vowel sounds. The precise mechanism behind this ability was not previously understood

After the birds hatched, the researchers trained them to peck keys in response to synthetic speech sounds that began with 'd' or 't'.

They then tested the birds' perception of speech sounds that varied in two cues: Voice onset time and the frequency of the first formant (formants are resonating frequencies of the vocal tract).

For comparison, they likewise tested the perception of speech sounds in 25 people.

The researchers found that, much like people, the budgerigars 'traded cues' that is, offset changes in one cue with those in another when perceiving speech sounds.

For example, when the first formant frequency differed, the birds identified 'd' when the voice onset time was short and 't' when it was long.

And this observed cue trading did not depend on prior experience with speech.

These findings support a general auditory mechanism for speech perception rather than one that is speech-specific.

'Regardless of their experience with speech sounds - whether completely isolated from human speech for their whole lives or trained extensively to mimic speech - the birds in our study used speech cues in a manner very similar to humans,' said Ms Flaherty.

'To the extent that birds can be used as a model for speech perception, these results indicate that prior experience with speech sounds is not a prerequisite for speech perception.'

There is something about human and bird auditory systems that integrates spectral and temporal information in a similar way, Ms Flaherty told MailOnline.

'Birds communicate with one another using sounds that also span the same frequencies as human speech (but also extend beyond what humans can produce),' she said.

'The results of the study suggest they use the same type of mechanism as humans to perceive these kinds of sounds.'